1. Field of the Invention
The present invention relates to new glucan derivatives having tumoricidal activity, and which are usable as medicines as tumoricides.
2. Discussion of the Background
Numerous natural polysaccharides or natural substances mainly comprising polysaccharides are being found to have tumoricidal activity. In particular, branches .beta.-1,3-glucans such as lentinan as well as BCG and constitutional components of tubercle bacillus are known to have strong tumoricidal activity. (See G. Chihara's "Cancers and Immunological Enhancement" by Kodan-sha Scientific, pp. 77-111, 1980.)
BCG comprises detoxicated live bacteria of bovine tubercle bacillus (Mycobacterium bovis), which are not absolutely safe. Therefore, extensive studies have been developed on a variety of extracts derived from cell walls of tubercle bacillus bacteria in attempts to obtain a safer product.
The polysaccharide components of the cell walls of tubercle bacillus bacteria are roughly classified into two groups. (See A. Misaki and I. Azuma's "Annual Report of the Sciences of Living, Osaka City University", 22, 33, 1981.) The first group comprises an .alpha.-(1.fwdarw.6)-mannan main chain with side chains of D-mannose, D-mannobiose, oligoarabianan (oligo-.alpha.-(1.fwdarw.5)-D-arabinofuranan). The second group comprises a .beta.-(1.fwdarw.4)-galactan main chain with a side chain of oligoarabinan. In particular, the latter is known to have higher tumoricidal activity.
But there is still a strongly felt need for substances which can be easily manufactured at a low cost, and which have low level toxicity and high tumoricidal activity.